Abstract

High-Frequency (HF) radars are operated in the 3-30 MHz frequency
range and need to share the frequency bands with other radio services.
Due to their Over-The-Horizon (OTH) capabilities, HF radars play an
important role in remote sensing and surveillance. The propagation
conditions of the electromagnetic wave depend on the earth's ionosphere
and mailnly follow a daily cycle. Communication paths between the HF radar and
other radio services, some thousands of kilometres off, open and close with
a high variability. Special care must be taken to dynamically adapt
the HF radar's characteristics to the varying electromagnetic environment.
The impact of a Frequency Modulated Continuous Wave (FMCW) HF radar on
other radio services is not very strong, because of its low transmit power
and utilisation of the radio spectrum. However, strong signals from
other radio services can significantly reduce the performance of the
oceanographic measurements.
Several radar control and signal processing steps are discussed in this
paper. All together form an effective procedure to reduce the impact of
Radio Frequency Interference (RFI) on the oceanographic measurements.
klaus-werner.gurgel@uni-hamburg.de